diff --git a/swh/indexer/storage/in_memory.py b/swh/indexer/storage/in_memory.py
--- a/swh/indexer/storage/in_memory.py
+++ b/swh/indexer/storage/in_memory.py
@@ -170,6 +170,7 @@
     def __init__(self):
         self._tools = {}
         self._mimetypes = SubStorage(self._tools)
+        self._languages = SubStorage(self._tools)
         self._content_ctags = SubStorage(self._tools)
         self._licenses = SubStorage(self._tools)
         self._content_metadata = SubStorage(self._tools)
@@ -253,6 +254,55 @@
         """
         yield from self._mimetypes.get(ids)
 
+    def content_language_missing(self, languages):
+        """List languages missing from storage.
+
+        Args:
+            languages (iterable): dictionaries with keys:
+
+                - **id** (bytes): sha1 identifier
+                - **indexer_configuration_id** (int): tool used to compute
+                  the results
+
+        Yields:
+            an iterable of missing id for the tuple (id,
+            indexer_configuration_id)
+
+        """
+        yield from self._languages.missing(languages)
+
+    def content_language_get(self, ids):
+        """Retrieve full content language per ids.
+
+        Args:
+            ids (iterable): sha1 identifier
+
+        Yields:
+            languages (iterable): dictionaries with keys:
+
+                - **id** (bytes): sha1 identifier
+                - **lang** (bytes): raw content's language
+                - **tool** (dict): Tool used to compute the language
+
+        """
+        yield from self._languages.get(ids)
+
+    def content_language_add(self, languages, conflict_update=False):
+        """Add languages not present in storage.
+
+        Args:
+            languages (iterable): dictionaries with keys:
+
+                - **id** (bytes): sha1
+                - **lang** (bytes): language detected
+
+            conflict_update (bool): Flag to determine if we want to
+                overwrite (true) or skip duplicates (false, the
+                default)
+
+        """
+        self._languages.add(languages, conflict_update)
+
     def content_ctags_missing(self, ctags):
         """List ctags missing from storage.
 
diff --git a/swh/indexer/tests/storage/test_in_memory.py b/swh/indexer/tests/storage/test_in_memory.py
--- a/swh/indexer/tests/storage/test_in_memory.py
+++ b/swh/indexer/tests/storage/test_in_memory.py
@@ -21,22 +21,6 @@
         pass
 
     @pytest.mark.xfail
-    def test_content_language_missing(self):
-        pass
-
-    @pytest.mark.xfail
-    def test_content_language_get(self):
-        pass
-
-    @pytest.mark.xfail
-    def test_content_language_add__drop_duplicate(self):
-        pass
-
-    @pytest.mark.xfail
-    def test_content_language_add__update_in_place_duplicate(self):
-        pass
-
-    @pytest.mark.xfail
     def test_origin_intrinsic_metadata_get(self):
         pass
 
diff --git a/swh/indexer/tests/test_language.py b/swh/indexer/tests/test_language.py
--- a/swh/indexer/tests/test_language.py
+++ b/swh/indexer/tests/test_language.py
@@ -7,8 +7,8 @@
 from swh.indexer import language
 from swh.indexer.language import LanguageIndexer
 from swh.indexer.tests.test_utils import (
-    BasicMockIndexerStorage, MockObjStorage, CommonContentIndexerTest,
-    CommonIndexerWithErrorsTest, CommonIndexerNoTool, BASE_TEST_CONFIG
+    CommonContentIndexerTest, CommonIndexerWithErrorsTest,
+    CommonIndexerNoTool, BASE_TEST_CONFIG, fill_storage, fill_obj_storage
 )
 
 
@@ -30,12 +30,6 @@
             }
         }
 
-    def prepare(self):
-        super().prepare()
-        self.idx_storage = BasicMockIndexerStorage()
-        self.objstorage = MockObjStorage()
-        self.tool_config = self.config['tools']['configuration']
-
 
 class Language(unittest.TestCase):
     """Tests pygments tool for language detection
@@ -60,8 +54,14 @@
     - Unknown sha1 in the input list are not indexed
 
     """
+
+    def get_indexer_results(self, ids):
+        yield from self.indexer.idx_storage.content_language_get(ids)
+
     def setUp(self):
         self.indexer = LanguageTestIndexer()
+        fill_storage(self.indexer.storage)
+        fill_obj_storage(self.indexer.objstorage)
 
         self.id0 = '02fb2c89e14f7fab46701478c83779c7beb7b069'
         self.id1 = '103bc087db1d26afc3a0283f38663d081e9b01e6'